The present invention relates to devices for reconditioning the cutting edges of cutting implements and, more particularly, devices for scoring corrugations along the beveled cutting edges of scissors' blades.
In sharpening the blades of hair cutting scissors, it is necessary to rescore corrugations along the cutting edges. The corrugations hold the hair and prevent the hair strands from sliding along the scissors' blades as the blades close to shear the hair, thereby making possible greater precision in performing a hair cutting operation. Repeated sharpening of the beveled cutting edges of corrugated scissors' blades wears away the corrugations, making it necessary to recorrugate the blades after sharpening.
Typically, corrugations are scored into the cutting edges of scissors' blades with a corrugating file in a process done by hand, with the result that the precision of the formation of corrugations is highly dependent upon the skill of the craftsman performing the filing operation in holding the file at the proper angle to the beveled edge and exerting a consistently sufficient downward force into the blade to form corrugations of the appropriate depth. Furthermore, as a result of this human element, the pressure and resultant depth of the scoring, the spacing of scoring, and other parameters will vary along a beveled edge of a scissors' blade as well as from one craftsman to the next. Accordingly, there is a need to provide a device which scores corrugations along the beveled cutting edges of scissors' blades with repeatable precision and with a predetermined filing force which results in an even depth of scoring along the cutting edge.
Attempts have been made to develop a device for forming serrations on scissors' blades, and an example of such a device is shown in Mikesell U.S. Pat. No. 966,036. That patent shows a serrating device in which a serrating file is held horizontally by a pivotal attachment at one end to a support rod and a pivotal attachment to a link arm at an opposite end. The link arm is pivotally attached to the support rod at a location spaced from the pivotal connection with the file. A clamp is used to hold the scissors' blade such that the beveled edge of the blade is substantially horizontal and parallel to the flat working underside of the file.
The sharpening process is conducted by oscillating the file in an arc having as its center the pivotal connection between the file end and the rod. Although this device provides a measure of uniformity in scoring serrations on a scissors' blade, there is no control over the downward force exerted by the user operating the file upon the beveled edge of the blade. As a result, the depth of the serrations may vary along the length of a cutting edge as well as from user to user.
In performing a corrugating operation upon a scissors' blade, it is desirable to move the file relative to the beveled edge in a direction which is perpendicular to the beveled cutting edge. If the file is moved in a direction skewed to the cutting edge, the scoring is less effective. Since the movement of the corrugating file in the aforementioned Mikesell patent is pivotal rather than linear, the direction of the file movement during a corrugating operation can only approximate a linear stroke.
There are analogous structures found in the scissors sharpening art. Exemplary of such devices are the sharpeners disclosed in Petrich U.S. Pat. No. 1,904,075; Foster U.S. Pat. No. 2,397,256; Garbarino U.S. Pat No. 2,557,093; and Eaton U.S. Pat. No. 1,681,763. In each of these devices, a scissors' blade is held in a clamp, vise or the like, and a file is drawn across the beveled cutting edge at an angle parallel to the beveled edge. The file is supported at one end by the sharpening device and is grasped by the user at the opposite end, so that the user must attempt to apply a consistent and sufficient downward pressure to effect the requisite frictional engagement between the working face of the file and the cutting edge of the scissors' blade. Again, the pressure exerted by the file upon the instrument to be sharpened in each of these devices will vary along the length of the scissors' blade as well as from user to user.
Accordingly, there is a need for a corrugating device which is capable of scoring corrugations in the beveled cutting edge of a scissors' blade in an accurate and repeatable manner. Furthermore, it is desirable to provide such a device with means for regulating the downward pressure of the file against the cutting edge, so that it remains within predictable limits, regardless of the skill of the user.